Intrinsic bending flexoelectric constants in two-dimensional materials

Abstract

Flexoelectricity is a form of electromechanical coupling that has recently emerged because, unlike piezoelectricity, it is theoretically possible in any dielectric material. Two-dimensional (2D) materials have also garnered significant interest because of their unusual electromechanical properties and high flexibility, but the intrinsic flexoelectric properties of these materials remain unresolved. In this work, using atomistic modeling accounting for charge-dipole interactions, we report the intrinsic flexoelectric constants for a range of two-dimensional materials, including graphene allotropes, nitrides, graphene analogs of group-IV elements, and the transition metal dichalcogenides (TMDCs). We accomplish this through a proposed mechanical bending scheme that eliminates the piezoelectric contribution to the total polarization, which enables us to directly measure the flexoelectric constants. While flat 2D materials like graphene have low flexoelectric constants due to weak $\pi -\sigma$ interactions, buckling is found to increase the flexoelectric constants in monolayer group-IV elements. Finally, due to significantly enhanced charge transfer coupled with structural asymmetry due to bending, the TMDCs are found to have the largest flexoelectric constants, including MoS${}_2$ having a flexoelectric constant ten times larger than graphene.

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Cited by in corpus (10)

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• High flexoelectric constants in Janus transition-metal dichalcogenides
• Outstandingly high thermal conductivity, elastic modulus, carrier mobility and piezoelectricity in two-dimensional semiconducting CrC2N4: A first-principles study
• Tuning flexoelectricty and electronic properties of zig-zag graphene nanoribbons by functionalization
• Properties of BSi${}_6$N monolayers derived by first-principle computation
• Flexoelectric radial polarization of single-walled nanotubes from first-principles
• Exploration of mechanical, thermal conductivity and electromechanical properties of graphene nanoribbon springs
• Dissecting intervalley coupling mechanisms in monolayer transition metal dichalcogenides
• Transversal flexoelectric coefficients for fifty select atomic monolayers from first principles